1. Field of the Invention
The present invention relates to inexpensive surface treated steel sheets having excellent rust resistance and weldability, suitable for manufacturing various kinds of cans. The surface treated steel sheets according to the present invention have excellent rust resistance and satisfactory weldability as surface treated without paint coatings, and hence can provide low-priced sheet material for cans, which can be used in actual service with or without paint coating after can welding.
2. Description of the Related Art
As sheet steel materials for various kinds of cans such as beverage cans, food cans, and aerosol cans, mainly tin-plates and tin-free steel (TFS) have been conventionally utilized, and more recently as sheet steel materials for welded cans, nickel-plated sheets with very thin nickel coating for lowering the production cost as disclosed in Japanese Patent Publication Sho 57-61829, Ni/Sn double layer coated steel sheets as disclosed in Japanese Patent Publication Sho 59-30798 and the like have been developed and actually put into practical use.
However, these conventional sheet materials, particularly tin-plates have disadvantage of high-cost due to the large consumption of high-priced tin, while the tin-free steel, though inexpensive, have the problem that welding cannot be performed without removing the surface film, and the new materials for the welded cans, namely the nickel coated sheets and Ni/Sn double layer coated sheets which have been developed for solving the above problems of the conventional tin-plates and TFS materials have been confronted with the problem of insufficient rust resistance, increasingly pointed out as a real problem in the can industry due to the thin coating which was originally contrived for lowering the production cost.
For these reasons, strong demand has been made by related industries for inexpensive new materials excellent in rust resistance and weldability.